论文标题
三角晶格上沮丧的$ t-t^\ prime $ hubbard模型中的磁性和自旋液相
Magnetic and spin-liquid phases in the frustrated $t-t^\prime$ Hubbard model on the triangular lattice
论文作者
论文摘要
Hubbard模型及其强耦合版本Heisenberg One已在三角形晶格上进行了广泛的研究，以捕获不同材料的基本低温性能。一个例子是过渡金属二分法源，为1T $ -TAS $ _2 $，其中一个带有$ 13 $ TAOM的大型单元形成弱耦合的层，以及各向同性三角形晶格。通过使用准确的变异蒙特卡洛计算，我们报告了三角晶格上$ t-t-t^\ prime $ hubbard模型的相图，突出了$ t^\ prime/t $的正值和负值之间的差异；只能通过包括有限电子电子排斥的始终存在的电荷波动来捕获该结果。检测到两个旋转液体区域：一个用于$ t^\ prime/t <0 $，持续到电子电子排斥的中间值，一个较窄的值，对于$ t^\ prime/t> 0 $。自旋液相似乎是无间隙的，尽管与海森堡极限相比，变化波函数具有列分特征。我们没有发现任何证据表明金属绝缘体跃迁的邻近性中的非磁性莫特阶段与预测有所不同（主要基于$ t/u $的强耦合膨胀），这表明存在弱摩托阶段，这些相位侵入金属和磁有序的绝缘子。
The Hubbard model and its strong-coupling version, the Heisenberg one, have been widely studied on the triangular lattice to capture the essential low-temperature properties of different materials. One example is given by transition metal dichalcogenides, as 1T$-$TaS$_2$, where a large unit cell with $13$ Ta atom forms weakly-coupled layers with an isotropic triangular lattice. By using accurate variational Monte Carlo calculations, we report the phase diagram of the $t-t^\prime$ Hubbard model on the triangular lattice, highlighting the differences between positive and negative values of $t^\prime/t$; this result can be captured only by including the charge fluctuations that are always present for a finite electron-electron repulsion. Two spin-liquid regions are detected: one for $t^\prime/t<0$, which persists down to intermediate values of the electron-electron repulsion, and a narrower one for $t^\prime/t>0$. The spin-liquid phase appears to be gapless, though the variational wave function has a nematic character, in contrast to the Heisenberg limit. We do not find any evidence for non-magnetic Mott phases in the proximity of the metal-insulator transition, at variance with the predictions (mainly based upon strong-coupling expansions in $t/U$) that suggest the existence of a weak-Mott phase that intrudes between the metal and the magnetically ordered insulator.
